Effect of titania content on the optical properties of dye-doped hybrid sol-gel coatings

Sol-gel waveguides have been realized using a mixture of zirconium and titanium alkoxides with 3-Glycidoxypropyltrimethoxysilane (Glymo) as organic modifier. The molar ratio metal (Ti,Zr)/Glymo was 70/30 in order to obtain a material with high refractive index. Coumarin30 dye was added into the matrix during the synthesis with a concentration 2 x 10(-2) M. optical properties have been investigated by spectroscopic ellipsometry and UV-visible absorption measurements. Crack free 600 runt thick coatings were obtained with refractive index in the range 1.56-1.66, increasing with the Ti-content. Steady-state and time-resolved fluorescence measurements evidenced an almost linear decrease of the Coumarin30 fluorescence efficiency as Ti-content increases. Such a behaviour can be related to an excited state quenching mechanism. (Zr-0.5-Ti-0.5)(70)/Glymo(30) coating could be considered a fair trade-off between wiveguiding performance (n = 1.61; 12 dB/cm) and Coumarin30 fluorescence efficiency. (C) 2008 Elsevier B.V. All rights reserved